Many large format avionics display systems incorporate touchscreen functionality, which allows a pilot to manipulate displayed images via direct finger contact with the display screen. Touchscreen functionality may be designed and built into a display system, but such a system is not retrofittable and must be highly customized, which is not ideal for lower-volume applications. In the alternative, touchscreen functionality may be implemented by applying touch sensors to the front surface of a display system. However, these touch sensors must be optically bonded to the front surface, which requires a clean room environment or presents the risk of contamination by foreign materials or other defects. In addition, as the touch sensors are bonded to the front surface of the display system (i.e., the surface proximate the pilot or viewer), the likelihood increases of the touch sensors adversely affecting image quality (ex.—reflectance, luminance) if expensive transparent materials are not used.
Further, digital resistive touch sensors commonly used for touchscreen applications require a border area around the perimeter of the display screen for connecting the touch matrix to the display drive electronics and controller system. This border area may create additional packaging cost and complexity while increasing display bezel width and constraining the use of large format display systems in smaller cockpits where available space is at a premium. It may therefore be desirable for a large format avionics display system to implement touchscreen functionality via sensors fixed to the rear surface of the display unit (i.e., the surface opposite the pilot or viewer).